Baked potatoes are allowed occasionally on the Zone diet.
No food is restricted on the Zone diet, according to the weight-management plan's creator, Barry Sears. However, if you want to lose weight, Sears advises eating foods that won't cause your insulin level to spike, which he believes is responsible for causing inflammation that leads to obesity. The Zone diet recommends eating meals that are 40 percent carbohydrate, 30 percent protein and 30 percent fat. On this plan, you're allowed to eat baked potatoes, but only occasionally, using a specific cooking method if you want your meal to have the smallest possible effect on your blood sugar.
Followers of the Zone diet are instructed to categorize foods as being "good" or "bad." Bad foods are fatty meats, full-fat dairy products, caffeinated drinks, alcohol and high-sugar or high-starch foods like potatoes. The good or bad designation is based primarily on the food's glycemic index, which measures how much it affects your blood sugar level. A food with a low glycemic index does not have a dramatic effect on your blood sugar, while one with a high glycemic index can cause a sharp spike your levels. Cooked white potatoes have a glycemic index over 80, which the Mayo Clinic defines as high glycemic index, so potatoes should be limited while you're on the Zone diet.
A 2005 study published in the "European Journal of Clinical Nutrition" reported that the glycemic index of cooked potatoes could be reduced by as much as 43 percent if they were eaten after being cooled. The researchers determined that the decreased glycemic index was due to the increased level of resistant starch in the cooled potatoes, a form of starch that is not broken down in the digestive system. They also found that tossing the cooled, cooked potatoes with a vinegar-based dressing further decreased the glycemic index. When you're on the Zone diet, eating baked potatoes cooled and mixed with a vinaigrette is the best way to keep your intake of foods with a high glycemic index under control.
Types of Potatoes
Another way to eat baked potatoes on the Zone diet is to use potatoes that have a low glycemic index. According to the Harvard Medical School, a medium-sized cooked sweet potato has a glycemic index of 70, and a cooked yam measures at only 54 on the glycemic index. In contrast, a study published in the "Journal of the American Dietetic Association" in 2005 reported that cooked red potatoes had the highest glycemic index of all types of cooked potatoes at 89.
The United States Potato Board points out that the way you serve a baked potato can significantly affect the glycemic index, making it a better fit for the Zone diet. Avoid mashing the flesh of baked potatoes, because that will increase the glycemic index. Eating a baked potato with a topping like salsa or vinegar will lower the glycemic index, as will eating it with lean protein like steak, chicken breast or fish.